Pam Blixt wrote: " ... The project will increase impervious surface
by 24 acres out of a total project size of 77 acres, much of which drains to
Diamond Lake. ... concerned about the effects of the highway project on
water quality ... "
Tom Holtzleiter wrote: " ... how will Diamond Lake be affected
exactly? Will it become filled with deiceing chemicals to the extent that
it will affect aquatic life? Will it flood? ... "
According to nationally recognized expert Fred Rozumalski, only about
10% of rainwater runs off into surface waters from a typical area of
naturally vegetated land in Minnesota. Approximately 40% evaporates and
approximately 50% infiltrates into the soil. Impermeable surfaces like paved
roads turn nature on its head. From these impermeable surfaces, generally
more than 98% of rainwater runs off into surface waters. This greatly
increased runoff amount does harm by washing into surface waters pollutant
substances such as gasoline, oil, and antifreeze drippings, road salt, and
dust. This type of runoff pollution is one of the main reasons for the
widespread deterioration of water quality in our lakes and rivers. We spend
millions every year building and maintaining treatment ponds to help reduce
this type of pollution, for instance, the new ponds next to Lake Calhoun and
Cedar Lake.
This 98%+ runoff from Impermeable surfaces also does harm by adding to
flood waters. A greatly increased amount of rain runs off very quickly,
instead of minimally and much more slowly from well vegetated land.
Another problem with impermeable surfaces is reduced recharge of
groundwater. Groundwater usually flows very slowly at only a few inches to a
few feet per year. Some groundwater eventually helps to recharge deep
aquifers. Some groundwater eventually seeps out into springs, wetlands,
lakes, rivers, creeks and ponds. The reduced groundwater recharge causes
many creeks to be lower than they should be during dry periods, and the
increased runoff causes creeks to be higher than they should be during wet
periods.
Many thanks to Pam Blixt for her concern and work to improve water
quality in Minneapolis.
Dave Stack
Harrison
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